The invention relates to microwave-stable tableware of siliceous material, such as porcelain, glass, stoneware, or ceramic. The term, "tableware," used herein, is to be understood to refer chiefly to plates, cups, platters, saucers, mugs, and drinking glasses.
A warning is stated in the operating instructions given by the manufacturers of microwave ovens which are used for heating foods, as well as in the technical literature, not to use tableware provided with metallic decoration, such as gold rims or the like, for heating foods in the microwave oven, because the decoration is destroyed by the effect of the microwave field, for example by electrical flashovers.
It is therefore the object of the present invention to create tableware of siliceous material provided with precious metal decoration which can be placed in a microwave oven for heating foods without destroying the precious metal decoration.
This problem is solved according to the invention, in microwave-stable tableware of the kind described above, in that it has precious metal decoration which consists of a pattern of markings, such as dots in which the distance between two adjacent dots amounts to at least 0.2 mm and the maximum extension of a dot amounts to 5 mm. Advantageously, the extension of a marking or dot is in the range from 0.3 to 4 mm. The precious metal decoration consists preferably of markings which are substantially equal in shape and/or size. The shape of the dots can be basically whatever is desired, as for example square, rectangular, circular, or elliptical.
Surprisingly, it has been found that tableware provided with precious metal decoration made in accordance with the invention can remain in the microwave field for any desired length of time--but at least for as long as it takes to cook a food that is on or in it--without destroying the precious metal decoration.
Precious metal decorations have proven especially durable which consist of markings with rounded margins, especially circular or elliptical markings or dots. Through the elimination of sharp corners the danger of electrical flashover and thus of the destruction of the decoration is even more greatly reduced.
The visual impression of the precious metal decoration made in accordance with the invention is especially good, i.e., the decoration strikes the human eye as being virtually "solid" if the sum of the areas of the markings amounts to about 60% of the total surface area of the decoration.
The thickness of a dot preferably ranges from 0.0001 to 0.1 mm, preferably from 0.0001 to 0.001 mm.
Any commercially available precious metal preparation can be used in producing the decoration; preparations containing gold, platinum, and palladium have proven especially desirable, such as bright gold, powdered gold, burnished gold or bright palladium, bright platinum, burnished platinum, or powdered platinum preparations which are fired onto the tableware. The precious metal preparation can be applied in the manner commonly known in the decorative art, for example by brush, feather, silk screen, direct printing or transfer printing, by stamping, or by an offset printing process.
Embodiments of the invention are represented in the drawings.